Impact of Styrene-Butadiene-Styrene (SBS) content on asphalt Binder's fatigue resistance at various aging levels using Viscoelastic Continuum Damage and fracture mechanics

The use Styrene-Butadiene-Styrene (SBS) modification of asphalt cement is considered as one of the effective ways to improve pavement performance. The increase in stiffness and the improved elastic response of the asphalt cement provide pavements with better rutting and fatigue resistance. On the other hand, cracking resistance in asphalt cement has proven to be a difficult property to evaluate. Several methods have been proposed, and one such method is the high strain Linear Amplitude Sweep (LAS) test using the dynamic shear rheometer, which has shown a good ability to evaluate cracking resistance in asphalt cement. The aim of this research is to examine the ability of different binder characterization techniques to distinguish the level of polymer modification in asphalt cements, as well as their ability to characterize fatigue resistance at different aging levels. Testing with the LAS has shown that the cycles to failure calculated using the Viscoelastic Continuum Damage Model correlate well with the concentration of SBS. The LAS can also be analyzed using fracture mechanics (Pure LAS) and this approach has also shown some correlation with SBS concentrations. The Pure LAS analysis has been shown to improve upon the characterization of different levels of laboratory aging. Finally, fatigue resistance of asphalt concrete specimens prepared with different levels of the SBS modification was studied using Four-Point Bending Beam test. A strong correlation was found between the results of asphalt cement LAS tests and fatigue testing of asphalt concrete mixtures. Both forms of analysis indicate that the LAS approach may provide good feedback when evaluating the role that SBS plays in improving the cracking resistance of asphalt cement. These are important developments for the characterization of cracking resistance in the asphalt binder which can lead to improved material selection for pavements.